Tectonic and magmatic processes along the transform margin of Southern Africa [Elektronische Ressource] / von Nicole Parsiegla

Nparsieg

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2009
• Nombre de lectures: 24
• Langue: English
• Poids de l'ouvrage: 22 Mo

Extrait

Tectonic and magmatic processes
along the transform margin of
southern Africa







Dissertation

zur Erlangung des Doktorgrades der Naturwissenschaften im Fachbereich
Geowissenschaften (FB 5) der Universität Bremen


von

Nicole Parsiegla







Bremerhaven, 2008












Stiftung Alfred-Wegener-Institut für Polar- und Meeresforschung in der
Helmholtzgemeinschaft




Table of contents

Zusammenfassung........................................................................................... 1
Abstract............................................................................................................. 5
1 Introduction................................................................................................. 7
1.1 Motivation and aims of this thesis........................................................................................ 7
1.2 Structure of the thesis .......................................................................................................... 9
2 Large Igneous Provinces ......................................................................... 13
2.1 The formation of Large Igneous Provinces........................................................................ 13
2.2 Large Igneous Provinces and climate................................................................................ 15
3 Geology and tectonic background.......................................................... 17
3.1 Geological overview of southern Africa and its offshore basins ........................................ 17
3.2 Continental margins of southern Africa.............................................................................. 22
4 Geoscientific concepts............................................................................. 25
4.1 Crustal stretching ............................................................................................................... 25
4.2 Processes at transform faults ............................................................................................ 26
5 The Agulhas Plateau: Structure and evolution of a Large Igneous
Province 29
Abstract ....................................................................................................................................... 29
Keywords.............. 29
5.1 Introduction ........................................................................................................................ 30
5.2 Geological and tectonic background.................................................................................. 32
5.3 Data acquisition and processing........................................................................................ 33
5.4 Modelling............................................................................................................................ 37
5.5 Crustal type and structure.................................................................................................. 44
5.6 The Agulhas Plateau LIP in a plate-tectonic context ......................................................... 48
5.7 Consequences of crustal generation ................................................................................. 50
5.8 Conclusions........................................................................................................................ 55
Acknowledgements ..................................................................................................................... 56
6 Deep crustal structure of the sheared South African continental
margin: first results of the Agulhas-Karoo Geoscience Transect ............. 57
Abstract ....................................................................................................................................... 57
Keywords.............. 58
6.1 Introduction ........................................................................................................................ 58
6.2 Tectonic framework............................................................................................................ 59
6.3 Seismic data acquisition .................................................................................................... 62
6.4 Data processing ................................................................................................................. 62
6.5 Data and modelling.. 63
6.6 Velocity-depth structure from the Agulhas Bank to the Agulhas Passage ........................ 67
6.7 Model quality...................................................................................................................... 70
6.8 Discussion.......................................................................................................................... 72
6.9 Conclusion....... 77
Acknowledgements...... 78
7 Crustal structure of the southern margin of the African continent:
Results from geophysical experiments........................................................ 79
Abstract ....................................................................................................................................... 79
7.1 Introduction ........................................................................................................................ 79
7.2 Profile setting ..................................................................................................................... 81
7.3 Seismic data acquisition .................................................................................................... 84
7.4 Wide-angle seismic data processing ................................................................................. 85
7.5 Results ............................................................................................................................... 89
7.6 Discussion.......................................................................................................................... 94
7.7 Summary..... 101
Acknowledgements ................................................................................................................... 102
8 The southern African continental margin – dynamic processes of a
transform margin.......................................................................................... 103
Abstract ..................................................................................................................................... 103
Keywords............ 104
8.1 Introduction ...................................................................................................................... 104
8.2 Geological and tectonic background................................................................................ 106
8.3 Seismic data acquisition, processing, and modelling ...................................................... 109
8.4 Seismic refraction and wide-angle reflection results and implications............................. 113
8.5 Crustal stretching and tectonic processes along/across the southern African margin.... 116
8.6 Geodynamic evolution of the margin ............................................................................... 123
8.7 Conclusions...................................................................................................................... 125
Acknowledgements: .................................................................................................................. 126
9 Conclusions and Outlook ...................................................................... 127
9.1 Conclusions..... 127
9.2 Outlook............................................................................................................................. 129
10 References ............................................................................................ 131
11 Acknowledgements .............................................................................. 151
12 Erklärung............................................................................................... 153
Zusammenfassung
Zusammenfassung

Als der Superkontinent Gondwana zerbrach, formten gigantische
Scherprozesse Afrikas südlichen Kontinentalrand. Sie wirkten entlang einer
mehr als 1000 km langen Transformstörung. Ihre Spur – die Agulhas-Falkland-
Bruchzone – erstreckt sich heutzutage vom Falklandplateau bis zum
südöstlichen Kontinentalrand Afrikas. Die Erforschung der Prozesse, welche die
Entstehung einer derart langen Transformstörung auslösten und während ihrer
aktiven Phase wirksam waren, ist notwendig, um zu verstehen, wie sich dieser
gescherte Kontinentalrand entwickelte. Afrikas südlicher Kontinentalrand ist
nicht nur eines der besten Beispiele, um die schmalen
Kontinentozeanübergangszonen, die Marginalrücken-, Bruchzonen- und
Beckenstrukturen, die mit Transformrändern in Verbindung gebracht werden, zu
untersuchen. Er bietet auch die einmalige Möglichkeit zu beleuchten, wie die
magmatischen Prozesse abliefen, die zur Bildung einer großen Eruptivprovinz
an einem gescherten Kontinentalrand führten. In dieser Doktorarbeit verwende
ich refraktionsseismische, reflexionsseismische Daten und plattentektonische
Re